Agricultural combines or “combine harvesters” are well-known for harvesting crops such as corn, soybeans, and wheat. The typical combine includes a self-propelled chassis supported on the ground via driving and driven wheels. A replaceable harvesting head is mounted on the front of the chassis for harvesting the crop of interest. The combine is operable to feed the harvested grain from the head to an internal threshing and separating system that separates the grain from stalks, pods, cobs, etc. (collectively referred to herein as “chaff”) and that transfers the grain to an on-board storage hopper. The stored grain can be periodically transferred to a wagon or the like by an auger mounted on the chassis adjacent the storage hopper.
So-called “split-torque” or “hydro-mechanical” transmissions have been proposed to address these and other problems encountered when driving a threshing rotor. U.S. Pat. Nos. 6,695,693 and 6,702,666 to Ho, Brome, and Bundy describe a combine in which an engine simultaneously drives the rotor through two power paths: (1) the engine drives a hydraulic pump, which drives a motor which drives the sun gear of a planetary gear set and (2) the engine drives a gear train which drives an engine-to-ring clutch which drives the ring gear of the planetary gear set.
The two paths are joined at a planetary gear box. The engine drives the ring gear. The motor drives the sun gear. The ring gear and sun gear drive the planetary gears. The planetary gears, in turn, drive the rotor.
One problem with these arrangements, however, is the failure of the rotor to slow down and stop rapidly when the engine-to-ring clutch is disengaged. At the end of a harvesting cycle, the operator manipulates an operator control in the operator's compartment such as a switch that causes the rotor electronic control system to uncouple (disengage) both the engine and motor from the rotor. When this happens, the rotor preferably coasts down from its operating speed of (typically) 250–1200 rpm to a complete stop.
Depending upon the internal friction in the system, the rotor may take a considerable amount of time, as much as several minutes, to slow to a halt. If the internal friction is insignificant, the rotor may indeed never stop rotating until the engine is turned off. Instead, the rotor may slowly rotate at a slow speed (30–100 rpm) until the operator is forced to shut off the engine.
This slow rotation is caused by fluid friction in the engine-to-ring clutch. The rotor control system disengages the engine-to-ring clutch when the operator turns the rotor off and thus there is no plate-to-plate contact. Nonetheless, the plates of the clutch are spaced closely enough to each other that the fluid in the clutch alone is enough to cause the engine to rotate the rotor very slowly.
When the operator shuts off the combine rotor, the operator expects it to stop promptly. When the rotor slows down to 30–100 rpm and keeps rotating indefinitely, the only choice the operator has is to shut off the engine and wait for the rotor to coast to a complete stop. Starting and stopping the engine causes unnecessary wear on a variety of components in the combine.
What is needed, therefore, is an improved method for decelerating and stopping the rotor of the combine. It is an object of this invention to provide such a method and apparatus.